1. Field of the Invention
The present invention relates to an electron emission display, and more particularly, to an electron emission display that can effectively focus electron beams emitted from electron emission regions by improving a focusing electrode.
2. Description of Related Art
In general, an electron emission element can be classified, depending upon the kind of electron source, into a hot cathode type or a cold cathode type.
There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements.
An FEA element includes electron emission regions and cathode and gate electrodes that are used as the driving electrodes. The electron emission regions are formed of a material having a relatively low work function and/or a relatively large aspect ratio, such as a molybdenum-based (Mo) material, a silicon-based (Si) material, and a carbon-based material such as carbon nanotubes (CNT), graphite, and diamond-like carbon (DLC) so that electrons can be effectively emitted when an electric field is applied to the electron emission regions under a vacuum atmosphere (or vacuum state). When the electron emission regions are formed of the molybdenum-base material or the silicon-based material, they are formed as a pointed tip structure.
The electron emission elements are arrayed on a first substrate to form an electron emission device. A light emission unit (having phosphor layers and an anode electrode) is formed on a second substrate. The first and second substrates, the electron emission device, and the light emission unit establish an electron emission display.
The electron emission device includes electron emission regions and a plurality of driving electrodes functioning as scanning and data electrodes. The electron emission regions and the driving electrodes control the on/off operation of each pixel and the amount of electrons emitted. The electrons emitted from the electron emission regions excite the phosphor layers to display an image (which may be predetermined).
The first and second substrates are sealed together at their peripheries using a sealing member, and the inner space between the first and second substrates is exhausted to form a vacuum envelope. In addition, a plurality of spacers are disposed in the vacuum envelope between the first and second substrates to prevent the substrates from being damaged or broken by a pressure difference between the inside and outside of the vacuum envelope.
The spacers are exposed to the internal space of the vacuum envelope in which electrons emitted from the electron emission regions move. The spacers are positively or negatively charged by the electrons colliding therewith. The charged spacers may distort the electron beam path by attracting or repulsing the electrons. As a result, a non-emission region of the phosphor layer increases.
For example, when the spacers are positively charged, the spacers attract the electrons such that a relatively large amount of electrons collides with a portion of the phosphor layer near the spacers. As a result, the luminance of the portion of the phosphor layer around the spacers is higher than the luminance of other portions. In this case, the spacers may be detected (observed) on a screen.
In order to reduce or prevent the distortion of the electron beam path, the spacers may be coated with an insulation material or may be connected to the electrodes to discharge the electric charges accumulated on the spacers.
However, due to defective connections between the spacers and the electrodes, the discharge of the electric charges is not effectively realized.